A magnetic disk device is provided with a write head including a main pole, write shield, and side shields. In the magnetic disk device, a recording current is applied to the write head, whereby a recording magnetic field is excited, and data is recorded onto a recording layer of the disk directly under the main pole of the write head. The side shields are formed integral with the write shield, and are positioned in the cross-track direction of the main pole. The side shields are magnetized in one direction in the cross-track direction. For this reason, in the write head, an easy direction of magnetization in which the magnetic flux of the recording magnetic field can easily flow, and a hard direction of magnetization in which the magnetic flux of the recording magnetic field can hardly flow exist in the cross-track direction.